Radeon HD 4890 2GB vs Radeon HD 6770

Intro

Compare those specs to the Radeon HD 6770, which comes with clock speeds of 900 MHz on the GPU, and 1050 MHz on the 512 MB of GDDR5 RAM. It features 800 SPUs along with 40 TAUs and 16 Rasterization Operator Units.

Display Graphs

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Power Usage and Theoretical Benchmarks

Power Consumption (Max TDP)

Radeon HD 6770		108 Watts
Radeon HD 4890 2GB		190 Watts
	Difference: 82 Watts (76%)

Memory Bandwidth

The Radeon HD 4890 2GB, in theory, should perform quite a bit faster than the Radeon HD 6770 overall. (explain)

Radeon HD 4890 2GB		124800 MB/sec
Radeon HD 6770		67200 MB/sec
	Difference: 57600 (86%)

Texel Rate

The Radeon HD 4890 2GB is a small bit (more or less 11%) more effective at anisotropic filtering than the Radeon HD 6770. (explain)

Radeon HD 4890 2GB		40000 Mtexels/sec
Radeon HD 6770		36000 Mtexels/sec
	Difference: 4000 (11%)

Pixel Rate

If using lots of anti-aliasing is important to you, then the Radeon HD 4890 2GB is superior to the Radeon HD 6770, though only just barely. (explain)

Radeon HD 4890 2GB		16000 Mpixels/sec
Radeon HD 6770		14400 Mpixels/sec
	Difference: 1600 (11%)

Please note that the above 'benchmarks' are all just theoretical - the results were calculated based on the card's specifications, and real-world performance may (and probably will) vary at least a bit.

Price Comparison

Specifications

Memory Bandwidth: Memory bandwidth is the largest amount of data (in units of MB per second) that can be transported across the external memory interface within a second. The number is calculated by multiplying the card's bus width by the speed of its memory. If it uses DDR type memory, it must be multiplied by 2 again. If DDR5, multiply by ANOTHER 2x. The higher the bandwidth is, the faster the card will be in general. It especially helps with anti-aliasing, HDR and higher screen resolutions.

Texel Rate: Texel rate is the maximum amount of texture map elements (texels) that can be applied in one second. This is worked out by multiplying the total texture units by the core speed of the chip. The better this number, the better the video card will be at handling texture filtering (anisotropic filtering - AF). It is measured in millions of texels per second.

Pixel Rate: Pixel rate is the most pixels the video card could possibly record to the local memory in a second - measured in millions of pixels per second. The figure is worked out by multiplying the number of Render Output Units by the the core clock speed. ROPs (Raster Operations Pipelines - also sometimes called Render Output Units) are responsible for outputting the pixels (image) to the screen. The actual pixel output rate is also dependant on many other factors, most notably the memory bandwidth - the lower the memory bandwidth is, the lower the potential to get to the max fill rate.